This invention relates to a method for manufacturing a molded article for use, for example, as a filter or as a preform for resin impregnation to form a structural composite.
U.S. patent application 858,974 discloses and claims a process for the manufacture of a fiber reinforced composite article. This composite article is manufactured from a nonwoven, airlaid batt, which is formed into a preform shape by molding before being injected with an appropriate resin to form the composite article. U.S. patent application 858,785 discloses a process in which a molded article is formed from an airlaid, nonwoven batt, which is then formed in a mold and can be used, for example, as a fluid filter. The nonwoven batts used in both processes are manufactured by techniques which are in general known to those skilled in the art, and the batts formed thereby may be pulled apart relatively easily. This is because, as the batt is formed, only the electrostatic forces between the fibers comprising the batt are relied upon to hold the batt together.
According to the above-identified application, a binder material is included in the batt which, upon being heated in an oven in which the batt was placed, at least partly melts the binder material, thus fusing the fibers in the batt, so that the batt could be handled. Although this process, in general, works well, it has been discovered that molding relatively thick batts into complex shapes was rendered difficult, because the batts had a tendency to buckle when they were molded into certain shapes. Accordingly, the batt became too stiff when the batt was heated until the binder material fused all the fibers in the batt, but the uncured batt was not stable enough to be molded and readily broke apart.